1. Field of the Invention
The present invention relates to a fuel injection valve, and to a technology of atomizing fuel and controlling the injecting direction.
2. Prior Art
Acceleration of atomization of fuel injected from a fuel injection valve and accurate control of the injecting direction are considered to be one of the most important problems to cope with improving fuel consumption and cleaning of exhaust gas of an internal combustion engine.
Japanese Patent Application Laid-Open No.61-234266 discloses a fuel injection system comprising a first main intake passage to be opened and closed by a first intake valve and a second main intake passage to be opened and closed by a second intake valve, the first main intake passage and the second main intake passage being opened to one of combustion chambers of an internal combustion engine; an opening-and-closing valve arranged in a main intake passage, the opening-and-closing valve being closed during low load operation and opened during high load operation; an auxiliary intake passage branched from the main intake passage at a position upstream of the opening-and-closing valve, the outlet end being opened to the first main intake passage at a position near the first intake valve, a passage area of the auxiliary passage being smaller than an area of the main intake passage; and a fuel injection system having a first injection hole and a second injection hole arranged in the main intake passage at positions downstream of the opening-and-closing valve, an injection path of the first injection hole being oriented so as to direct the injection to the first intake valve, an injection path of the second injection hole being oriented so as to direct the injection to the second intake valve.
Further, the above-referenced Japanese published application discloses that a diffusion angle of the injection path in the second injection hole is set smaller than a diffusion angle of the injection path in the first injection hole, and an amount of fuel injection through the first injection hole is set larger than an amount of fuel injection through the second injection hole. Furthermore, in the fuel injection valve, the opening area of the both injection holes are different from each other in order to make the amounts of fuel injection from the both injection holes different from each other.
Japanese Patent Application Laid-Open No.8-218986 discloses a fuel injection system comprising a fuel injection valve for injecting fuel spray inside an intake pipe, the fuel injection valve being arranged at a position upstream side of an intake valve in the intake pipe of an internal combustion engine, wherein an injection portion of the fuel injection valve comprises at least one injection hole having a curved nearly semi-arc shape and, further, the fuel injection valve is arranged so that an outermost peripheral portion of the spray is within a range of a tangent line connecting between a wall surface of an intake port and the injecting portion and may collide against an area within a back surface of the intake valve.
In the above-mentioned conventional technology, two sprays are injected from one fuel injection valve toward two directions so that each of the two sprays may be injected onto a respective one of two intake ports provided in one combustion chamber. However, fuel atomization forming the spray at that time is not sufficiently considered.
In addition, in the case where fuel is sprayed in the two directions, the traveling time until the spray reaches the combustion chamber (hereinafter, referred to as “transport time”) is not always the same between the two sprays due to the deviation of intake flow rate and the resistance of flow passage caused by the structure and the shape of the intake passage. Otherwise, the structure and the shape of the intake passage (intake pipe) may be restricted by intending to make the transport time equal between the two sprays.
In the above-mentioned conventional technology, the time lag in the traveling time until the spray reaches the combustion chamber between the two sprays (hereinafter, referred to as “transport lag”) is not considered. In the first of the above-mentioned two Japanese published applications, the diffusion angle of spray is made different between the first injection hole and the second injection hole but, however, without having considered varying the penetration of each spray. The penetration of spray varies depending on the degree of atomization of fuel composing the spray and, consequently, the penetration of spray can not be uniquely determined from an amount of fuel injection or an initial speed of injected fuel.